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1. Technical Field
This invention relates to compositions for cleaning glassware. More particularly, it relates to glassware cleaning compositions for use in automatic dishwashing machines of the Industrial and Institutional (IandI) type wherein the compositions afford glassware protection.
2. Background Art
Compositions for use in dishwashing wherein the compositions afford glassware protection are well known. These are described in U.S. Pat. Nos. 2,575,576; 3,255,117; 3,350,318; 4,416,794 and 4,443,270 which teach the use of soluble zinc salts for this purpose. In U.S. Pat. No. 2,575,576 a water soluble zinc salt is employed to prevent the corrosion of vitreous and ceramic surfaces. In U.S. Pat. Nos. 3,255,117 and 3,350,318 soluble zinc salts are described for use in automatic dishwashing detergent compositions. In U.S. Pat. No. 3,677,820 it is taught that solid plates of zinc metal alloys are placed in contact with the use concentration of the detergent composition where the metal zinc slowly dissolves, and thereby needs occasional replacement to provide corrosion protection to glassware. A soluble zinc salt is disclosed in U.S. Pat. No. 4,443,270 in conjunction with a low foaming nonionic surfactant and in U.S. Pat. No. 4,416,794 zinc salts of chloride, sulfate or acetate are taught.
In U.S. Pat. Nos. 4,908,148 and 4,933,101 insoluble inorganic zinc compounds are employed in conjunction with a surfactant. However, relatively large amounts of the insoluble inorganic zinc compounds are required. Further, the inorganic compounds are suspended in the form of highly viscous liquids or slurries which present problems as further explained herein.
Notwithstanding the teachings of the prior art, there is a need for an improved liquid automatic dishwashing composition which can provide efficient cleaning in fast cycle IandI dishwashing machines yet provide glassware protection.
Accordingly, the advantages of the invention are:
a. Providing an improved dishwashing composition.
b. Providing an improved dishwashing composition for use with fast cycle IandI dishwashing machines which have previously required highly corrosive alkaline materials.
c. Providing an improved dishwashing composition of the foregoing kind which utilize minimal amounts of zinc salts.
d. Providing an improved method of utilizing the foregoing kind wherein the zinc salt is low in toxicity.
e. Providing an improved method of utilizing the foregoing composition.
The foregoing advantages are accomplished by the dishwashing composition of this invention which includes in one embodiment a chelate, an alkaline producing material, and a soluble zinc organic salt.
In another embodiment, the zinc salt is zinc gluconate, zinc formate or zinc acetate.
In a preferred embodiment, the zinc salt is zinc gluconate.
In still another preferred embodiment the liquid automatic dishwashing detergent composition includes from 15% to about 75% of a chelate, from about 5% to about 25% of an alkaline producing material and from about 2% to about 10% of a soluble zinc organic salt.
In yet another preferred embodiment the chelate is present in an amount of about 30% to about 70%, the alkaline producing material is present in an amount of about 7% to about 15%, and the zinc organic salt is present in an amount of about 3% to about 5%.
In still another preferred embodiment the chelate includes an organic phosphonate polymer.
In one aspect a method of washing glassware is provided employing the composition of this invention and in a preferred manner in conjunction with a rinsing agent having a nonionic surfactant.
In another aspect the zinc gluconate is formed in an in situ process step.
In yet another aspect zinc and gluconate ions are provided in the dishwashing detergent composition by zinc and gluconate salts.
Further aspects and advantages of the invention will become apparent from the description of the preferred embodiments which follows: